It seems kinda redundant to have booting and boot separate; although one is a verb and one is a noun, it seems like it would be simpler to keep them under one tag (for organization's sake).
I'm suggesting bootup (3) & booting (49) -> boot (343)
[multi-boot] and [dual-boot] also need to be merged, but I'm not sure which one needs to be kept.
Much like the more-than-one-monitor tags ([dual-monitors] and [multiple-monitors], which were merged into [multiple-monitors]), we really don't need two different tags for the concept of "more than one". I think [multiple-monitors] works pretty well, and I'd prefer to keep [multi-boot] as the more general term. But I'm afraid [dual-boot] is more common and more widely-known.